@@ -87,7 +87,7 @@ class DotWidget(Gtk.DrawingArea):

         self.x, self.y = 0.0, 0.0

         self.zoom_ratio = 1.0

-        self.zoom_to_fit_on_resize = False

+        self.zoom_to_fit_on_resize_reload = False

         self.animation = animation.NoAnimation(self)

         self.drag_action = actions.NullAction(self)

         self.presstime = None

@@ -165,7 +165,7 @@ class DotWidget(Gtk.DrawingArea):

         parser = XDotParser(xdotcode, graphviz_version=self.graphviz_version)

         self.graph = parser.parse()

-        self.zoom_image(self.zoom_ratio, center=center)

+        self.queue_draw()

     def reload(self):

         if self.openfilename is not None:

@@ -177,6 +177,8 @@ class DotWidget(Gtk.DrawingArea):

                 pass

             else:

                 del self.history_back[:], self.history_forward[:]

+                if self.zoom_to_fit_on_resize_reload:

+                    self.zoom_to_fit()

     def update(self):

         if self.openfilename is not None:

@@ -250,7 +252,7 @@ class DotWidget(Gtk.DrawingArea):

             self.x += x / self.zoom_ratio - x / zoom_ratio

             self.y += y / self.zoom_ratio - y / zoom_ratio

         self.zoom_ratio = zoom_ratio

-        self.zoom_to_fit_on_resize = False

+        self.zoom_to_fit_on_resize_reload = False

         self.queue_draw()

     def zoom_to_area(self, x1, y1, x2, y2):

@@ -264,7 +266,7 @@ class DotWidget(Gtk.DrawingArea):

                 float(rect.width)/float(width),

                 float(rect.height)/float(height)

             )

-        self.zoom_to_fit_on_resize = False

+        self.zoom_to_fit_on_resize_reload = False

         self.x = (x1 + x2) / 2

         self.y = (y1 + y2) / 2

         self.queue_draw()

@@ -280,7 +282,7 @@ class DotWidget(Gtk.DrawingArea):

             float(rect.height)/float(self.graph.height)

         )

         self.zoom_image(zoom_ratio, center=True)

-        self.zoom_to_fit_on_resize = True

+        self.zoom_to_fit_on_resize_reload = True

     ZOOM_INCREMENT = 1.25

     ZOOM_TO_FIT_MARGIN = 12

@@ -468,7 +470,7 @@ class DotWidget(Gtk.DrawingArea):

         return True

     def on_area_size_allocate(self, area, allocation):

-        if self.zoom_to_fit_on_resize:

+        if self.zoom_to_fit_on_resize_reload:

             self.zoom_to_fit()

     def animate_to(self, x, y):

@@ -599,10 +599,10 @@ class DotWindow(Gtk.Window):

             ('Reload', Gtk.STOCK_REFRESH, None, None, "Reload graph", self.on_reload),

             ('Print', Gtk.STOCK_PRINT, None, None,

              "Prints the currently visible part of the graph", self.dotwidget.on_print),

-            ('ZoomIn', Gtk.STOCK_ZOOM_IN, None, None, None, self.dotwidget.on_zoom_in),

-            ('ZoomOut', Gtk.STOCK_ZOOM_OUT, None, None, None, self.dotwidget.on_zoom_out),

-            ('ZoomFit', Gtk.STOCK_ZOOM_FIT, None, None, None, self.dotwidget.on_zoom_fit),

-            ('Zoom100', Gtk.STOCK_ZOOM_100, None, None, None, self.dotwidget.on_zoom_100),

+            ('ZoomIn', Gtk.STOCK_ZOOM_IN, None, None, "Zoom in", self.dotwidget.on_zoom_in),

+            ('ZoomOut', Gtk.STOCK_ZOOM_OUT, None, None, "Zoom out", self.dotwidget.on_zoom_out),

+            ('ZoomFit', Gtk.STOCK_ZOOM_FIT, None, None, "Fit zoom", self.dotwidget.on_zoom_fit),

+            ('Zoom100', Gtk.STOCK_ZOOM_100, None, None, "Reset zoom level", self.dotwidget.on_zoom_100),

             ('FindNext', Gtk.STOCK_GO_FORWARD, 'Next Result', None, 'Move to the next search result', self.on_find_next),

         ))

@@ -126,7 +126,6 @@ class DotWidget(Gtk.DrawingArea):

             sys.stderr.write(error + '\n')

         if p.returncode != 0:

             self.error_dialog(error)

-            return None

         return xdotcode

     def _set_dotcode(self, dotcode, filename=None, center=True):

@@ -355,6 +355,9 @@ class DotWidget(Gtk.DrawingArea):

             toolbar = win.uimanager.get_widget("/ToolBar")

             toolbar.set_visible(not toolbar.get_visible())

             return True

+        if event.keyval == Gdk.KEY_w:

+            self.zoom_to_fit()

+            return True

         return False

     print_settings = None

@@ -640,7 +640,7 @@ class DotWindow(Gtk.Window):

         # Add Find text search

         find_toolitem = uimanager.get_widget('/ToolBar/Find')

-        self.textentry = Gtk.Entry(max_length=20)

+        self.textentry = Gtk.Entry()

         self.textentry.set_icon_from_stock(0, Gtk.STOCK_FIND)

         find_toolitem.add(self.textentry)

@@ -592,9 +592,9 @@ class DotWindow(Gtk.Window):

         # Create actions

         actiongroup.add_actions((

-            ('Open', Gtk.STOCK_OPEN, None, None, None, self.on_open),

-            ('Export', Gtk.STOCK_SAVE_AS, None, None, "Save graph as picture.", self.on_export),

-            ('Reload', Gtk.STOCK_REFRESH, None, None, None, self.on_reload),

+            ('Open', Gtk.STOCK_OPEN, None, None, "Open dot-file", self.on_open),

+            ('Export', Gtk.STOCK_SAVE_AS, None, None, "Export graph to other format", self.on_export),

+            ('Reload', Gtk.STOCK_REFRESH, None, None, "Reload graph", self.on_reload),

             ('Print', Gtk.STOCK_PRINT, None, None,

              "Prints the currently visible part of the graph", self.dotwidget.on_print),

             ('ZoomIn', Gtk.STOCK_ZOOM_IN, None, None, None, self.dotwidget.on_zoom_in),

@@ -766,12 +766,23 @@ class DotWindow(Gtk.Window):

         subprocess.check_call(cmd)

     def on_export(self, action):

+        

+        if self.dotwidget.openfilename is None:

+            return

+        

+        default_filter = "PNG image"

+    

         output_formats = {

+            "dot file": "dot",

+            "GIF image": "gif",

+            "JPG image": "jpg",

+            "JSON": "json",

+            "PDF": "pdf",

             "PNG image": "png",

+            "PostScript": "ps",

             "SVG image": "svg",

-            "PDF image": "pdf",

-            "GIF image": "gif",

-            "PDF image": "pdf",

+            "XFIG image": "fig",

+            "xdot file": "xdot",

         }

         buttons = (

             Gtk.STOCK_CANCEL, Gtk.ResponseType.CANCEL,

@@ -793,7 +804,9 @@ class DotWindow(Gtk.Window):

             filter_.set_name(name)

             filter_.add_pattern('*.' + ext)

             chooser.add_filter(filter_)

-        

+            if name == default_filter:

+                chooser.set_filter(filter_)

+

         if chooser.run() == Gtk.ResponseType.OK:

             filename = chooser.get_filename()

             format_ = output_formats[chooser.get_filter().get_name()]

@@ -133,6 +133,7 @@ class DotWidget(Gtk.DrawingArea):

         # By default DOT language is UTF-8, but it accepts other encodings

         assert isinstance(dotcode, bytes)

         xdotcode = self.run_filter(dotcode)

+            

         if xdotcode is None:

             return False

         try:

@@ -155,6 +156,7 @@ class DotWidget(Gtk.DrawingArea):

     def set_xdotcode(self, xdotcode, center=True):

         assert isinstance(xdotcode, bytes)

+

         if self.graphviz_version is None:

             stdout = subprocess.check_output([self.filter, '-V'], stderr=subprocess.STDOUT)

             stdout = stdout.rstrip()

@@ -537,6 +539,7 @@ class DotWindow(Gtk.Window):

     <ui>

         <toolbar name="ToolBar">

             <toolitem action="Open"/>

+            <toolitem action="Export"/>

             <toolitem action="Reload"/>

             <toolitem action="Print"/>

             <separator/>

@@ -590,6 +593,7 @@ class DotWindow(Gtk.Window):

         # Create actions

         actiongroup.add_actions((

             ('Open', Gtk.STOCK_OPEN, None, None, None, self.on_open),

+            ('Export', Gtk.STOCK_SAVE_AS, None, None, "Save graph as picture.", self.on_export),

             ('Reload', Gtk.STOCK_REFRESH, None, None, None, self.on_reload),

             ('Print', Gtk.STOCK_PRINT, None, None,

              "Prints the currently visible part of the graph", self.dotwidget.on_print),

@@ -749,6 +753,55 @@ class DotWindow(Gtk.Window):

             self.open_file(filename)

         else:

             chooser.destroy()

+   

+    def export_file(self, filename, format_):

+        if not filename.endswith("." + format_):

+            filename += '.' + format_

+        cmd = [

+            self.dotwidget.filter, # program name, usually "dot"

+            '-T' + format_,

+            '-o', filename,

+            self.dotwidget.openfilename,

+        ]

+        subprocess.check_call(cmd)

+

+    def on_export(self, action):

+        output_formats = {

+            "PNG image": "png",

+            "SVG image": "svg",

+            "PDF image": "pdf",

+            "GIF image": "gif",

+            "PDF image": "pdf",

+        }

+        buttons = (

+            Gtk.STOCK_CANCEL, Gtk.ResponseType.CANCEL,

+            Gtk.STOCK_SAVE, Gtk.ResponseType.OK)

+        chooser = Gtk.FileChooserDialog(

+            parent=self,

+            title="Export to other file format.",

+            action=Gtk.FileChooserAction.SAVE,

+            buttons=buttons) 

+        chooser.set_default_response(Gtk.ResponseType.OK)

+        chooser.set_current_folder(self.last_open_dir)

+        

+        openfilename = os.path.basename(self.dotwidget.openfilename)

+        openfileroot = os.path.splitext(openfilename)[0]

+        chooser.set_current_name(openfileroot)

+

+        for name, ext in output_formats.items():

+            filter_ = Gtk.FileFilter()

+            filter_.set_name(name)

+            filter_.add_pattern('*.' + ext)

+            chooser.add_filter(filter_)

+        

+        if chooser.run() == Gtk.ResponseType.OK:

+            filename = chooser.get_filename()

+            format_ = output_formats[chooser.get_filter().get_name()]

+            chooser.destroy()

+            self.export_file(filename, format_)

+        else:

+            chooser.destroy()

+	

     def on_reload(self, action):

         self.dotwidget.reload()

@@ -725,7 +725,7 @@ class DotWindow(Gtk.Window):

     def on_open(self, action):

         chooser = Gtk.FileChooserDialog(parent=self,

-                                        title="Open dot File",

+                                        title="Open Graphviz File",

                                         action=Gtk.FileChooserAction.OPEN,

                                         buttons=(Gtk.STOCK_CANCEL,

                                                  Gtk.ResponseType.CANCEL,

@@ -734,7 +734,8 @@ class DotWindow(Gtk.Window):

         chooser.set_default_response(Gtk.ResponseType.OK)

         chooser.set_current_folder(self.last_open_dir)

         filter = Gtk.FileFilter()

-        filter.set_name("Graphviz dot files")

+        filter.set_name("Graphviz files")

+        filter.add_pattern("*.gv")

         filter.add_pattern("*.dot")

         chooser.add_filter(filter)

         filter = Gtk.FileFilter()

@@ -568,6 +568,7 @@ class DotWindow(Gtk.Window):

         window.set_title(self.base_title)

         window.set_default_size(width, height)

+        window.set_wmclass("xdot", "xdot")

         vbox = Gtk.VBox()

         window.add(vbox)

@@ -56,6 +56,7 @@ class DotWidget(Gtk.DrawingArea):

     }

     filter = 'dot'

+    graphviz_version = None

     def __init__(self):

         Gtk.DrawingArea.__init__(self)

@@ -100,6 +101,7 @@ class DotWidget(Gtk.DrawingArea):

     def set_filter(self, filter):

         self.filter = filter

+        self.graphviz_version = None

     def run_filter(self, dotcode):

         if not self.filter:

@@ -153,7 +155,14 @@ class DotWidget(Gtk.DrawingArea):

     def set_xdotcode(self, xdotcode, center=True):

         assert isinstance(xdotcode, bytes)

-        parser = XDotParser(xdotcode)

+        if self.graphviz_version is None:

+            stdout = subprocess.check_output([self.filter, '-V'], stderr=subprocess.STDOUT)

+            stdout = stdout.rstrip()

+            mo = re.match(br'^.* - .* version (?P<version>.*) \(.*\)$', stdout)

+            assert mo

+            self.graphviz_version = mo.group('version').decode('ascii')

+

+        parser = XDotParser(xdotcode, graphviz_version=self.graphviz_version)

         self.graph = parser.parse()

         self.zoom_image(self.zoom_ratio, center=center)

@@ -73,7 +73,8 @@ class DotWidget(Gtk.DrawingArea):

         self.add_events(Gdk.EventMask.POINTER_MOTION_MASK |

                         Gdk.EventMask.POINTER_MOTION_HINT_MASK |

                         Gdk.EventMask.BUTTON_RELEASE_MASK |

-                        Gdk.EventMask.SCROLL_MASK)

+                        Gdk.EventMask.SCROLL_MASK |

+                        Gdk.EventMask.SMOOTH_SCROLL_MASK)

         self.connect("motion-notify-event", self.on_area_motion_notify)

         self.connect("scroll-event", self.on_area_scroll_event)

         self.connect("size-allocate", self.on_area_size_allocate)

@@ -439,9 +440,13 @@ class DotWidget(Gtk.DrawingArea):

             self.zoom_image(self.zoom_ratio * self.ZOOM_INCREMENT,

                             pos=(event.x, event.y))

             return True

-        if event.direction == Gdk.ScrollDirection.DOWN:

+        elif event.direction == Gdk.ScrollDirection.DOWN:

             self.zoom_image(self.zoom_ratio / self.ZOOM_INCREMENT,

                             pos=(event.x, event.y))

+        else:

+            deltas = event.get_scroll_deltas()

+            self.zoom_image(self.zoom_ratio * (1 - deltas.delta_y / 10),

+                            pos=(event.x, event.y))

             return True

         return False

@@ -672,6 +672,7 @@ class DotWindow(Gtk.Window):

         dot_widget = self.dotwidget

         if not entry_text:

             dot_widget.set_highlight(None, search=True)

+            self.set_focus(self.dotwidget)

             return

         found_items = self.find_text(entry_text)

@@ -20,6 +20,7 @@ import re

 import subprocess

 import sys

 import time

+import operator

 import gi

 gi.require_version('Gtk', '3.0')

@@ -534,6 +535,10 @@ class DotWindow(Gtk.Window):

             <toolitem action="Zoom100"/>

             <separator/>

             <toolitem name="Find" action="Find"/>

+            <separator name="FindNextSeparator"/>

+            <toolitem action="FindNext"/>

+            <separator name="FindStatusSeparator"/>

+            <toolitem name="FindStatus" action="FindStatus"/>

         </toolbar>

     </ui>

     '''

@@ -577,6 +582,7 @@ class DotWindow(Gtk.Window):

             ('ZoomOut', Gtk.STOCK_ZOOM_OUT, None, None, None, self.dotwidget.on_zoom_out),

             ('ZoomFit', Gtk.STOCK_ZOOM_FIT, None, None, None, self.dotwidget.on_zoom_fit),

             ('Zoom100', Gtk.STOCK_ZOOM_100, None, None, None, self.dotwidget.on_zoom_100),

+            ('FindNext', Gtk.STOCK_GO_FORWARD, 'Next Result', None, 'Move to the next search result', self.on_find_next),

         ))

         self.back_action = Gtk.Action('Back', None, None, Gtk.STOCK_GO_BACK)

@@ -593,6 +599,10 @@ class DotWindow(Gtk.Window):

                                          "Find a node by name", None)

         actiongroup.add_action(find_action)

+        findstatus_action = FindMenuToolAction("FindStatus", None,

+                                               "Number of results found", None)

+        actiongroup.add_action(findstatus_action)

+

         # Add the actiongroup to the uimanager

         uimanager.insert_action_group(actiongroup, 0)

@@ -619,6 +629,15 @@ class DotWindow(Gtk.Window):

         self.textentry.connect("activate", self.textentry_activate, self.textentry);

         self.textentry.connect("changed", self.textentry_changed, self.textentry);

+        uimanager.get_widget('/ToolBar/FindNextSeparator').set_draw(False)

+        uimanager.get_widget('/ToolBar/FindStatusSeparator').set_draw(False)

+        self.find_next_toolitem = uimanager.get_widget('/ToolBar/FindNext')

+        self.find_next_toolitem.set_sensitive(False)

+

+        self.find_count = Gtk.Label()

+        findstatus_toolitem = uimanager.get_widget('/ToolBar/FindStatus')

+        findstatus_toolitem.add(self.find_count)

+

         self.show_all()

     def find_text(self, entry_text):

@@ -628,9 +647,11 @@ class DotWindow(Gtk.Window):

         for element in dot_widget.graph.nodes + dot_widget.graph.edges:

             if element.search_text(regexp):

                 found_items.append(element)

-        return found_items

+        return sorted(found_items, key=operator.methodcaller('get_text'))

     def textentry_changed(self, widget, entry):

+        self.find_index = 0

+        self.find_next_toolitem.set_sensitive(False)

         entry_text = entry.get_text()

         dot_widget = self.dotwidget

         if not entry_text:

@@ -639,8 +660,14 @@ class DotWindow(Gtk.Window):

         found_items = self.find_text(entry_text)

         dot_widget.set_highlight(found_items, search=True)

+        if found_items:

+            self.find_count.set_label('%d nodes found' % len(found_items))

+        else:

+            self.find_count.set_label('')

     def textentry_activate(self, widget, entry):

+        self.find_index = 0

+        self.find_next_toolitem.set_sensitive(False)

         entry_text = entry.get_text()

         dot_widget = self.dotwidget

         if not entry_text:

@@ -649,8 +676,9 @@ class DotWindow(Gtk.Window):

         found_items = self.find_text(entry_text)

         dot_widget.set_highlight(found_items, search=True)

-        if(len(found_items) == 1):

+        if found_items:

             dot_widget.animate_to(found_items[0].x, found_items[0].y)

+        self.find_next_toolitem.set_sensitive(len(found_items) > 1)

     def set_filter(self, filter):

         self.dotwidget.set_filter(filter)

@@ -717,6 +745,15 @@ class DotWindow(Gtk.Window):

         dlg.run()

         dlg.destroy()

+    def on_find_next(self, action):

+        self.find_index += 1

+        entry_text = self.textentry.get_text()

+        # Maybe storing the search result would be better

+        found_items = self.find_text(entry_text)

+        found_item = found_items[self.find_index]

+        self.dotwidget.animate_to(found_item.x, found_item.y)

+        self.find_next_toolitem.set_sensitive(len(found_items) > self.find_index + 1)

+

     def on_history(self, action, has_back, has_forward):

         self.back_action.set_sensitive(has_back)

         self.forward_action.set_sensitive(has_forward)

@@ -336,6 +336,12 @@ class DotWidget(Gtk.DrawingArea):

         if event.keyval == Gdk.KEY_p:

             self.on_print()

             return True

+        if event.keyval == Gdk.KEY_t:

+            # toggle toolbar visibility

+            win = widget.get_toplevel()

+            toolbar = win.uimanager.get_widget("/ToolBar")

+            toolbar.set_visible(not toolbar.get_visible())

+            return True

         return False

     print_settings = None

@@ -168,7 +168,10 @@ class DotWidget(Gtk.DrawingArea):

     def update(self):

         if self.openfilename is not None:

-            current_mtime = os.stat(self.openfilename).st_mtime

+            try:

+                current_mtime = os.stat(self.openfilename).st_mtime

+            except OSError:

+                return True

             if current_mtime != self.last_mtime:

                 self.last_mtime = current_mtime

                 self.reload()

@@ -50,7 +50,8 @@ class DotWidget(Gtk.DrawingArea):

     # TODO GTK3: Second argument has to be of type Gdk.EventButton instead of object.

     __gsignals__ = {

         'clicked': (GObject.SIGNAL_RUN_LAST, None, (str, object)),

-        'error': (GObject.SIGNAL_RUN_LAST, None, (str,))

+        'error': (GObject.SIGNAL_RUN_LAST, None, (str,)),

+        'history': (GObject.SIGNAL_RUN_LAST, None, (bool, bool))

     }

     filter = 'dot'

@@ -89,6 +90,8 @@ class DotWidget(Gtk.DrawingArea):

         self.presstime = None

         self.highlight = None

         self.highlight_search = False

+        self.history_back = []

+        self.history_forward = []

     def error_dialog(self, message):

         self.emit('error', message)

@@ -160,6 +163,8 @@ class DotWidget(Gtk.DrawingArea):

                 fp.close()

             except IOError:

                 pass

+            else:

+                del self.history_back[:], self.history_forward[:]

     def update(self):

         if self.openfilename is not None:

@@ -439,9 +444,39 @@ class DotWidget(Gtk.DrawingArea):

             self.zoom_to_fit()

     def animate_to(self, x, y):

+        del self.history_forward[:]

+        self.history_back.append(self.get_current_pos())

+        self.history_changed()

+        self._animate_to(x, y)

+

+    def _animate_to(self, x, y):

         self.animation = animation.ZoomToAnimation(self, x, y)

         self.animation.start()

+    def history_changed(self):

+        self.emit(

+            'history',

+            bool(self.history_back),

+            bool(self.history_forward))

+

+    def on_go_back(self, action=None):

+        try:

+            item = self.history_back.pop()

+        except LookupError:

+            return

+        self.history_forward.append(self.get_current_pos())

+        self.history_changed()

+        self._animate_to(*item)

+

+    def on_go_forward(self, action=None):

+        try:

+            item = self.history_forward.pop()

+        except LookupError:

+            return

+        self.history_back.append(self.get_current_pos())

+        self.history_changed()

+        self._animate_to(*item)

+

     def window2graph(self, x, y):

         rect = self.get_allocation()

         x -= 0.5*rect.width

@@ -481,6 +516,9 @@ class DotWindow(Gtk.Window):

             <toolitem action="Reload"/>

             <toolitem action="Print"/>

             <separator/>

+            <toolitem action="Back"/>

+            <toolitem action="Forward"/>

+            <separator/>

             <toolitem action="ZoomIn"/>

             <toolitem action="ZoomOut"/>

             <toolitem action="ZoomFit"/>

@@ -507,6 +545,7 @@ class DotWindow(Gtk.Window):

         self.dotwidget = widget or DotWidget()

         self.dotwidget.connect("error", lambda e, m: self.error_dialog(m))

+        self.dotwidget.connect("history", self.on_history)

         # Create a UIManager instance

         uimanager = self.uimanager = Gtk.UIManager()

@@ -531,6 +570,16 @@ class DotWindow(Gtk.Window):

             ('Zoom100', Gtk.STOCK_ZOOM_100, None, None, None, self.dotwidget.on_zoom_100),

         ))

+        self.back_action = Gtk.Action('Back', None, None, Gtk.STOCK_GO_BACK)

+        self.back_action.set_sensitive(False)

+        self.back_action.connect("activate", self.dotwidget.on_go_back)

+        actiongroup.add_action(self.back_action)

+

+        self.forward_action = Gtk.Action('Forward', None, None, Gtk.STOCK_GO_FORWARD)

+        self.forward_action.set_sensitive(False)

+        self.forward_action.connect("activate", self.dotwidget.on_go_forward)

+        actiongroup.add_action(self.forward_action)

+

         find_action = FindMenuToolAction("Find", None,

                                          "Find a node by name", None)

         actiongroup.add_action(find_action)

@@ -658,3 +707,7 @@ class DotWindow(Gtk.Window):

         dlg.set_title(self.base_title)

         dlg.run()

         dlg.destroy()

+

+    def on_history(self, action, has_back, has_forward):

+        self.back_action.set_sensitive(has_back)

+        self.forward_action.set_sensitive(has_forward)

@@ -169,17 +169,26 @@ class DotWidget(Gtk.DrawingArea):

                 self.reload()

         return True

+    def _draw_graph(self, cr, rect):

+        w, h = float(rect.width), float(rect.height)

+        cx, cy = 0.5 * w, 0.5 * h

+        x, y, ratio = self.x, self.y, self.zoom_ratio

+        x0, y0 = x - cx / ratio, y - cy / ratio

+        x1, y1 = x0 + w / ratio, y0 + h / ratio

+        bounding = (x0, y0, x1, y1)

+

+        cr.translate(cx, cy)

+        cr.scale(ratio, ratio)

+        cr.translate(-x, -y)

+        self.graph.draw(cr, highlight_items=self.highlight, bounding=bounding)

+

     def on_draw(self, widget, cr):

         rect = self.get_allocation()

         Gtk.render_background(self.get_style_context(), cr, 0, 0,

                               rect.width, rect.height)

         cr.save()

-        cr.translate(0.5*rect.width, 0.5*rect.height)

-        cr.scale(self.zoom_ratio, self.zoom_ratio)

-        cr.translate(-self.x, -self.y)

-

-        self.graph.draw(cr, highlight_items=self.highlight)

+        self._draw_graph(cr, rect)

         cr.restore()

         self.drag_action.draw(cr)

@@ -342,13 +351,8 @@ class DotWidget(Gtk.DrawingArea):

     def draw_page(self, operation, context, page_nr):

         cr = context.get_cairo_context()

-

         rect = self.get_allocation()

-        cr.translate(0.5*rect.width, 0.5*rect.height)

-        cr.scale(self.zoom_ratio, self.zoom_ratio)

-        cr.translate(-self.x, -self.y)

-

-        self.graph.draw(cr, highlight_items=self.highlight)

+        self._draw_graph(cr, rect)

     def get_drag_action(self, event):

         state = event.state

@@ -170,11 +170,11 @@ class DotWidget(Gtk.DrawingArea):

         return True

     def on_draw(self, widget, cr):

-        cr.set_source_rgba(1.0, 1.0, 1.0, 1.0)

-        cr.paint()

+        rect = self.get_allocation()

+        Gtk.render_background(self.get_style_context(), cr, 0, 0,

+                              rect.width, rect.height)

         cr.save()

-        rect = self.get_allocation()

         cr.translate(0.5*rect.width, 0.5*rect.height)

         cr.scale(self.zoom_ratio, self.zoom_ratio)

         cr.translate(-self.x, -self.y)

@@ -122,23 +122,23 @@ class DotWidget(Gtk.DrawingArea):

             return None

         return xdotcode

-    def _set_dotcode(self, dotcode, filename=None):

+    def _set_dotcode(self, dotcode, filename=None, center=True):

         # By default DOT language is UTF-8, but it accepts other encodings

         assert isinstance(dotcode, bytes)

         xdotcode = self.run_filter(dotcode)

         if xdotcode is None:

             return False

         try:

-            self.set_xdotcode(xdotcode)

+            self.set_xdotcode(xdotcode, center=center)

         except ParseError as ex:

             self.error_dialog(str(ex))

             return False

         else:

             return True

-    def set_dotcode(self, dotcode, filename=None):

+    def set_dotcode(self, dotcode, filename=None, center=True):

         self.openfilename = None

-        if self._set_dotcode(dotcode, filename):

+        if self._set_dotcode(dotcode, filename, center=center):

             if filename is None:

                 self.last_mtime = None

             else:

@@ -146,17 +146,17 @@ class DotWidget(Gtk.DrawingArea):

             self.openfilename = filename

             return True

-    def set_xdotcode(self, xdotcode):

+    def set_xdotcode(self, xdotcode, center=True):

         assert isinstance(xdotcode, bytes)

         parser = XDotParser(xdotcode)

         self.graph = parser.parse()

-        self.zoom_image(self.zoom_ratio, center=True)

+        self.zoom_image(self.zoom_ratio, center=center)

     def reload(self):

         if self.openfilename is not None:

             try:

                 fp = open(self.openfilename, 'rb')

-                self._set_dotcode(fp.read(), self.openfilename)

+                self._set_dotcode(fp.read(), self.openfilename, center=False)

                 fp.close()

             except IOError:

                 pass

@@ -122,8 +122,7 @@ class DotWidget(Gtk.DrawingArea):

             return None

         return xdotcode

-    def set_dotcode(self, dotcode, filename=None):

-        self.openfilename = None

+    def _set_dotcode(self, dotcode, filename=None):

         # By default DOT language is UTF-8, but it accepts other encodings

         assert isinstance(dotcode, bytes)

         xdotcode = self.run_filter(dotcode)

@@ -135,6 +134,11 @@ class DotWidget(Gtk.DrawingArea):

             self.error_dialog(str(ex))

             return False

         else:

+            return True

+

+    def set_dotcode(self, dotcode, filename=None):

+        self.openfilename = None

+        if self._set_dotcode(dotcode, filename):

             if filename is None:

                 self.last_mtime = None

             else:

@@ -152,7 +156,7 @@ class DotWidget(Gtk.DrawingArea):

         if self.openfilename is not None:

             try:

                 fp = open(self.openfilename, 'rb')

-                self.set_dotcode(fp.read(), self.openfilename)

+                self._set_dotcode(fp.read(), self.openfilename)

                 fp.close()

             except IOError:

                 pass

@@ -113,9 +113,9 @@ class DotWidget(Gtk.DrawingArea):

             p = subprocess.CalledProcessError(exc.errno, self.filter, exc.strerror)

         else:

             xdotcode, error = p.communicate(dotcode)

+            error = error.decode()

         error = error.rstrip()

         if error:

-            error = error.decode()

             sys.stderr.write(error + '\n')

         if p.returncode != 0:

             self.error_dialog(error)

@@ -124,8 +124,8 @@ class DotWidget(Gtk.DrawingArea):

     def set_dotcode(self, dotcode, filename=None):

         self.openfilename = None

-        if isinstance(dotcode, str):

-            dotcode = dotcode.encode('utf-8')

+        # By default DOT language is UTF-8, but it accepts other encodings

+        assert isinstance(dotcode, bytes)

         xdotcode = self.run_filter(dotcode)

         if xdotcode is None:

             return False

@@ -151,7 +151,7 @@ class DotWidget(Gtk.DrawingArea):

     def reload(self):

         if self.openfilename is not None:

             try:

-                fp = open(self.openfilename, 'rt')

+                fp = open(self.openfilename, 'rb')

                 self.set_dotcode(fp.read(), self.openfilename)

                 fp.close()

             except IOError:

@@ -607,7 +607,7 @@ class DotWindow(Gtk.Window):

     def open_file(self, filename):

         try:

-            fp = open(filename, 'rt')

+            fp = open(filename, 'rb')

             self.set_dotcode(fp.read(), filename)

             fp.close()

         except IOError as ex:

@@ -39,8 +39,8 @@ from gi.repository import Gdk

 from . import actions

 from ..dot.lexer import ParseError

 from ..dot.parser import XDotParser

-from .animation import NoAnimation, ZoomToAnimation

-from .actions import NullAction, PanAction, ZoomAction, ZoomAreaAction

+from . import animation

+from . import actions

 from .elements import Graph

@@ -84,8 +84,8 @@ class DotWidget(Gtk.DrawingArea):

         self.x, self.y = 0.0, 0.0

         self.zoom_ratio = 1.0

         self.zoom_to_fit_on_resize = False

-        self.animation = NoAnimation(self)

-        self.drag_action = NullAction(self)

+        self.animation = animation.NoAnimation(self)

+        self.drag_action = actions.NullAction(self)

         self.presstime = None

         self.highlight = None

         self.highlight_search = False

@@ -298,7 +298,7 @@ class DotWidget(Gtk.DrawingArea):

             return True

         if event.keyval == Gdk.KEY_Escape:

             self.drag_action.abort()

-            self.drag_action = NullAction(self)

+            self.drag_action = actions.NullAction(self)

             return True

         if event.keyval == Gdk.KEY_r:

             self.reload()

@@ -351,12 +351,12 @@ class DotWidget(Gtk.DrawingArea):

         if event.button in (1, 2):  # left or middle button

             modifiers = Gtk.accelerator_get_default_mod_mask()

             if state & modifiers == Gdk.ModifierType.CONTROL_MASK:

-                return ZoomAction

+                return actions.ZoomAction

             elif state & modifiers == Gdk.ModifierType.SHIFT_MASK:

-                return ZoomAreaAction

+                return actions.ZoomAreaAction

             else:

-                return PanAction

-        return NullAction

+                return actions.PanAction

+        return actions.NullAction

     def on_area_button_press(self, area, event):

         self.animation.stop()

@@ -389,7 +389,7 @@ class DotWidget(Gtk.DrawingArea):

     def on_area_button_release(self, area, event):

         self.drag_action.on_button_release(event)

-        self.drag_action = NullAction(self)

+        self.drag_action = actions.NullAction(self)

         x, y = int(event.x), int(event.y)

         if self.is_click(event):

             el = self.get_element(x, y)

@@ -431,7 +431,7 @@ class DotWidget(Gtk.DrawingArea):

             self.zoom_to_fit()

     def animate_to(self, x, y):

-        self.animation = ZoomToAnimation(self, x, y)

+        self.animation = animation.ZoomToAnimation(self, x, y)

         self.animation.start()

     def window2graph(self, x, y):

@@ -47,10 +47,10 @@ from .elements import Graph

 class DotWidget(Gtk.DrawingArea):

     """GTK widget that draws dot graphs."""

-    #TODO GTK3: Second argument has to be of type Gdk.EventButton instead of object.

+    # TODO GTK3: Second argument has to be of type Gdk.EventButton instead of object.

     __gsignals__ = {

-        'clicked' : (GObject.SIGNAL_RUN_LAST, None, (str, object)),

-        'error' : (GObject.SIGNAL_RUN_LAST, None, (str,))

+        'clicked': (GObject.SIGNAL_RUN_LAST, None, (str, object)),

+        'error': (GObject.SIGNAL_RUN_LAST, None, (str,))

     }

     filter = 'dot'